It is known that in rolling stands for flat products, such as metal strip or sheet, in particular for delicate and high quality materials such as aluminum or suchlike, cleaning units are used, which comprise brushes for cleaning the surface of the rolling rolls.
The operation to clean the surface of the rolling rolls is carried out to prevent small residues of material, which remain adherent to the surfaces of the rolls, from causing defects in the flat metal products during rolling.
Indeed, such residues could cause unwanted marks such as impressions, furrows or scratches on the delicate metal materials like aluminum for example.
It is known that the brushes used for cleaning the surface of rolling rolls are not always kept in contact with the latter, but for practical reasons, for part of the time in which rolling is carried out, they remain in contact with the rolling roll, thus cleaning its surface.
Positioning devices for cleaning units for rolling rolls are known which, to take the brushes into contact with the rolling roll, or to distance them from it, use a mobile support body, such as for example a movable slide, on which a corresponding brush is mounted.
The movable slide is moved in a radial direction with respect to the rolling rolls, using one or more hydraulic actuators.
Positioning devices for cleaning units for rolling rolls are also known, for example that shown in U.S. Pat. No. 5,531,090, in which the brushes are mounted on a chock that supports a corresponding work roll while the movement device is a hydraulic actuator mounted inside the rolling stand, by driving which the brushes are moved nearer to/distanced from the rolling roll.
In such positioning devices for cleaning units for rolling rolls, the brushes can be positioned by radial or rotation movements in which their axis is displaced substantially parallel with respect to the axis of the rolling roll.
Furthermore, state-of-the-art positioning devices for cleaning units for rolling rolls use systems with many mechanical elements interacting with each other, which lead to strong plays being generated in the mechanisms, to the detriment of accuracy in positioning.
The assembly of state-of-the-art positioning devices for cleaning units for rolling rolls, in particular in the solution with a radially movable slide, requires inevitable plays between the support frame of the brushes and the corresponding guides.
Such plays cause vibrations in the part of the mobile support that lead to consequent vibrations of the brush as well.
One disadvantage due to the vibrations of the brush is the marking of the rolling roll, which can cause consequent signs and marking in the surface of the rolled product, which is even more accentuated as the wear progresses on the support frame of the brushes and the corresponding guides.
Another disadvantage of state-of-the-art positioning devices for cleaning units for rolling rolls is due to their excessive size and bulk, which do not allow easy installation and make the maintenance operations of the rolling stands more difficult.
Another disadvantage is that known positioning devices are not easily adaptable to different positions of the brush, which can be required to adapt the cleaning steps to the progressive wear of the rolling rolls due to friction between the surfaces and/or due to a grinding operation.
Other examples of cleaning units for rolling rolls are described in WO-A-2008/017412, JP-A-2010.184254, JP-A-H06.304615 and U.S. Pat. No. 4,852,209.
For example, WO-A-2008/017412 describes cleaning rolls for rolling rolls, for hot rolling aluminum. In this known solution, a brush is installed on a support body. The support body and the brush are moved by a hydraulic cylinder through a transmission element and an adjustment element. The hydraulic cylinder is pivoted around a pin. However, this solution does not allow to overcome the disadvantages described above.
There is therefore a need to perfect a rolling stand comprising a cleaning unit of a rolling roll that can overcome at least one of the disadvantages of the state of the art.
In particular, one purpose of the present invention is to obtain a cleaning unit that is compact and therefore not bulky inside the rolling stand.
Another purpose of the present invention is to perfect a rolling stand provided with a positioning device that allows to reduce, or even eliminate, the vibrations transmitted to the brush.
Another purpose of the present invention is to obtain a rolling stand in which the cleaning unit is positioned precisely, reliably and long-lastingly.
Another purpose of the present invention is to obtain a rolling stand in which the cleaning unit is practical and efficient.
Another purpose of the present invention is to obtain a rolling stand that is easy to adjust, to adapt to variable circumferences of the rolling rolls, also as a consequence of the progressive wear during working.
Moreover, one purpose of the present invention is to obtain a rolling stand with a positioning device that is simple and economical.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.